Resistance welding apparatus

ABSTRACT

Resistance welding apparatus of the type providing a pair of electrodes between which welding current may be passed through stock disposed between the electrodes. One of the electrodes aforesaid is a roller electrode which bears against and rolls along the stock to be welded and the other is an elongated backup electrode extending in the direction of travel of the roller electrode.

United States Patent Richard N. Karl Cortland;

Francis A. Bodenheim, Warren, Ohio 796,498

Feb. 4, 1969 Feb. 9, 1971 The McKay Machine Company Youngstown, OhioInventors Appl. No. Filed Patented Assignee RESISTANCE WELDING APPARATUSReferences Cited UNITED STATES PATENTS 1,282,502 10/1918 WagneretalPrimary ExaminerJ. V, Truhe Assistant ExaminerHugh D. JaegerAttorney-Williams and Kreske ABSTRACT: Resistance welding apparatus ofthe type providing a pair of electrodes between which welding currentmay be passed through stock disposed between the electrodes. One of theelectrodes aforesaid is a roller electrode which bears against and rollsalong the stock to be welded and the other is w an elongated backupelectrode extending in the direction of travel of the roller electrode.

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INVENTORS FRANus A-BODENHEW'I 4M RICHARD N- KARL 1 WW A ATTORNE/sPREAMBLE While welding apparatus of the type hereinabove described ingin considerable production loss and attendant high manufacturing costs.

SUMMARY In contrast, the present invention provides apparatus in which abackup electrode provides a multitude of working surfaces which can bepresented for use as required in a moments time by the machine operatorwithout requiring the attendance of a maintenance man or other skilledperson. This is accomplished by rotatably mounting the backup electrodebetween axially spaced members and by frictionally restraining thebackup electrode against rotation during normal use. Not only do thefrictional supporting members restrain rotation of the backupelectrodes, they also provide means by which welding current is fedthereto.

Since the backup electrode may gradually be reduced in transverse sizeas a result of dressing operations which restore its working surfaceswhen they are no longer serviceable, the frictional supporting membersand the supported backup electrode are selectively movable in adirection toward the roller electrode to maintain a constant pass lineof the apparatus despite a decreasing transverse size of the backupelectrode.

Cost and space limitations normally dictate a backup electrode which isrelatively small in transverse section and, to prevent excessivedeflection of the backup electrode under the pressure exerted by theroller electrode, the backup electrode may be supported intermediate thefrictional supporting members. Because of the progressive reduction intransverse size of the backup electrode as it is dressed, theintennediate support is selectively movable in a direction toward theroller electrode to properly support the backup electrode despite itsdecreasing transverse size.

Finally, to facilitate dressing of the backup electrode-when its workingsurfaces are no longer serviceable without necessitating removal of suchelectrode from its normal use position, an electrode dressing device isprovided which is selectively movable toward and away from electrodedressing position and is movable longitudinally of the electrode wherebyits entire working length may be dressed.

These and other advantages of the present invention will readily becomeapparent from a study of the following description and from the appendeddrawings, and in these drawings:

DRAWING DESCRIPTION FIG. I is a fragmentary side elevational view ofapparatus embodying the present invention, portions on the near sidebeing broken away to show the underlying structure;

FIG. 2 is a front elevational view of the apparatus seen in FIG. 1,portions on the near side here again being broken away;

FIG. 3 is a fragmentary sectional view generally corresponding to theline 3-3 of FIG. 2;

FIG. 4 is a transverse sectional view generally corresponding to theline4-4ofFlG. l;

FIG. 5 is a view similar to FIG 4 but showing certain parts in anotherposition; and

FIG. 6 is a reduced size, perspective view of certain details.

DETAILED DESCRIPTION With reference to FIGS. 1 and 2, a roller electrode10 is mounted on any conventional carriage (not shown) for movement fromleft to right in the position of parts seen in FIG. I. Underlying rollerelectrode 10 is a backup electrode 11 which extends along the path oftravel of the roller electrode. ln Operation, stock S to be welded willbe disposed in superposed relation on the backup electrode 11 and theroller electrode 10 will be caused to transverse the stock with apredetermined amount of downward pressure while welding current iscaused to flow between the electrodes and through the interpositionedstock.

Since both of the electrodes 10, 11 are normally formed of materialhaving high electrical conductivity such as copper, the working surfacesthereof; that is, the surfaces in contact with the stock which aresubjected to heavy current, high temperature and heavy welding pressure,tend to deteriorate quite rapidly. Deterioration of the electrodesworking surfaces results in inferior welds and for this reason, it haslong been common practice to provide electrode-dressing means or tootherwise restore the working surface of the electrode.

With respect to the roller electrode 10, much prior art is devoted toapparatus for maintaining the working periphery thereof in optimumconditions and, since it forms no part of the present invention, nomeans have been shown for maintaining the periphery of roller electrode10. It will be understood, of course, that any suitable prior artstructure may conveniently be used for this purpose.

Moreover, while a roller electrode 10 has herein been disclosed, it isto be understood that a spot-welding electrode and its supporting headcould be substituted for the roller electrode and its carriage, suchelectrode traveling along the stock by intermittent movement andperforming a spot-welding operation while its movement aforesaid isarrested. Since the present invention, however, is concerned withmaintaining an optimum working surface of the backup electrode 11, thisdisclosure is primarily directed to the structure which eliminates theproblems attendant with the backup electrodes of prior art apparatus.

As herein disclosed, backup electrode 11 is in the form of an elongatedbar which, in the preferred embodiment illustrated, is round in crosssection. As best seen in FIGS. 1, 2 and 3, one end of electrode 11 isseated in an upwardly facing pocket 13 in a slide member 14. An insert15 of high electrical conductivity lines the pocket 13 and isconfigurated to closely fit with the electrode 11. A cap member 16,having a downwardly directed recess 17 is secured to the slide member14. The recess in cap member 16 is lined with a dielectric insert 18 toelectrically insulate the cap member from the electrode. Insert 18, likeinsert 15, is configurated to closely fit with the electrode 11.

As seen in FIG. 3, cap member 16 is removably secured to the slidemember 14 by capscrews 19 having compression springs 20 underlying thecapscrew heads. The arrangement is such that while the electrode 11 isfirmly gripped between the slide member 14 and the cap member 16, thesprings 20 so limit gripping pressure that the electrode may be rotatedwithin the bearing provided by the slide 14 and the cap 16 by theapplication of sufficient torque to overcome frictional resistance ofthe bearing. To retain electrode 11 against axial movement, axiallyspaced retainer rings 21 may be disposed in suitable grooves in theelectrode thus providing shoulders which bear against opposed faces ofthe slide member and its cap member.

Still referring to FIGS. 1, 2 and 3, slide member 14 is verticallyslidable in a guide member 22 having upstanding guide legs 22.1, 22.3and 22.4 at respective comers of the slide member for guiding movementof the latter. Guide member 22 provides a flat surface 23 along which awedge 24 is slidable between the guide member leg pairs 22.1, 22.2 and22.3, 22.4. Wedge 24 fits between depending legs 25 of the slide member14 and inclined surface 26 of the wedge bears against a correspondinginclined surface 27 on the slide member 14. As best seen in FIG. 1, aboss 28 projects forwardly of guide member 22 and secured to such bossis a vertically extending plate 29. .loumaled in an upward extension ofplate 29 is a threaded shaft 30 which passes between the guidemember legpairs 22.1, 22.2 and 22.3, 22.4, and has threaded engagement with thewedge 24. A hand wheel 31 provides for rotation of the shaft 30 and thusmovement of the wedge 24 along the guide member surface 23.

Means are provided for maintaining slide member 14 seated upon the wedge24 and as herein disclosed, a pair of elongated studs 32 (see especiallyFIG. 3) are anchored in the slide member and depend therefrom forextension through respective enlarged apertures in the guide member 22.Secured across the studs 32 by nuts 33 is a crossbar 34 and acompression spring 35 is interposed between the cross bar 34 and theguide member 22 to exert a resilient downward force on the slide member14.

As best seen in FIGS. 1 and 2, slide member 14 is provided with a boss36 projecting between the guide member pair of legs 22.2, 22.3 and suchboss has an angled face 37 to which one end of a flexible electricallead 38 is secured. The other end of lead 38 is secured to a rearwardlyextending bus bar 39, in turn secured to the guide member 22 by bolts40. In the usual manner, insulating material 41 may electrically isolateth a bus bar 39 from the guide member 22.

Although not shown, the rear or opposite end of backup electrode 11 willbe supported in an identical manner as is the end thus far described,the shaft 30 having operable connection with the wedge of such rearassembly whereby rotation of such shaft simultaneously effects identicalmovement of the front and rear slide members. Accordingly, opposite endsof the backup electrode will be simultaneously raised and lowered byrotation of the hand wheel 31. Moreover, it will be understood that thebus bar 39 is secured to the rear guide member in the same manner as itis secured to the front guide member-22 and a flexible lead identical tolead 38 establishes an electrical connection from the rear of bus bar 39to the rear slide member. Also not shown is the usual weldingtransformer which, in an any convenient manner, will have one outputlead connected to the bus bar 39 and its other output lead connected tothe roller electrode 10.

Since the backup electrode 11 may frequently be of considerable lengthwhile its diameter is rather small, means are provided for supportingthe intermediate portion of ,the backup electrode against deflectioncaused by the roller electrode traveling therealong. As seen in FIGS. 1and 4, a bracket 42 is secured to the bus bar 39 in any suitable mannerwhich will electrically isolate the bracket from the bar. Rotatablysupported by the bracket 42 is one end of a shaft 43 whose other end isjournaled in the lower extension of the previously mentioned plate 29.

Afflxed to the shaft 43 adjacent the bracket 42 is a miter gear 44 whichis meshed with a miter gear 45. Affixed to gear 45 is an upstanding stubshaft 46 whose upper portion has threaded engagement with an upstandingsupport leg 47 which is vertically slideable within the bracket 42.Support leg 47 is slotted at 48 to clear the previously mentioned shaft30 and the upper end of the support leg is grooved at 49 to cradle thebackup electrode. Affrxed to the shaft 43 adjacent the plate 29 is ahand wheel 50 by means of which shaft 43 may be rotated.

From the foregoing, it will be understood that rotation of shaft 43will, through the miter gears 44, 45 rotate the stub shaft 46 and, sincethe latter has threaded connection with the support leg 47, will raiseor lower the latter as required.

After a number of welding operations have been performed by theapparatus hereinabove described, the precise number being dependent uponthe material being welded, the welding current being used, the requiredquality of weld, and many other factors too varied to enumerate, thatportion of backup electrode 11 which immediately underlies the rollerelectrode (see FIG. 6) will deteriorate, as indicated by the referencecharacter A, to the point where satisfactory welds can no longer bemade. When this occurs, a tool may be inserted in one of the holes 51 inthe backup electrode 11 and the latter will be rotated an amountsufficient to present an undamaged surface for cooperation with theroller electrode 10. Welding may now proceed until the necessity forexposure of another backup electrode surface arises.

The backup electrode 11 may continue to be indexed as required in themanner above described until such time as the entire usable peripheralsurface of the electrodeis no longer suitable for use. When this occurs,the backup electrode may be removed from the machine by removing thefront and rear cap members 16. Such worn electrode may now be machinedby cutting away its damaged periphery. The machined backup electrode maynowbe reassembled with the machine; however, since its diameter is nowless than that of before, as

shown somewhat exaggerated in FIG. 5, the electrode will be raised, byrotation of shaft 30, so as to maintain its upper working surface in thesame plane as before. With the electrode thus raised, support leg 47will also be raised, by proper rotation of shaft 43, to supportingrelation with the electrode.

Welding may once again proceed, along with periodic in dexing of thebackup electrode as before described, until such time as the entire,usable peripheral surface of the electrode is once again unsuitable foruse whereupon the electrode may be machined once again. The foregoingoperations may proceed as required until such time as further machiningof the backup electrode is impractical whereupon such electrode will bereplaced by a new one.

To reduce still further the necessity for frequent machining of thebackup electrode, a dressing device such as shown in FIG. 4 may beincorporated for removing pickup from the electrode such as may beencountered when welding aluminum or tinned, galvanized or otherwisecoated metals.

Mounted for movement along the bus bar 39, as by means of flangedrollers 52, is a carriage 53 supporting a housing 54. Such housingmounts an electrode dressing wheel 55 driven by a suitable motor 56.Spaced, parallel links 57, 57 secure housing 54 to the carriage formovement between its fullline position wherein the dressing wheel 55 isspaced from the backup electrode to its phantom line position whereinthe dressing wheel abuts the electrode. Although not shown, any suitablemechanism may be provided for effecting housing movement aforesaid.

Normally, of course, the dressing device is disposed in its full lineposition where it will not interfere with welding operations nor withrotation of the backup electrode as previously described. When, however,the device is to be used, motor 56 will be activated to drive thedressing wheel 55 and the housing will be shifted to its phantom lineposition to engage the electrode with the dressing wheel. Assuming thatcarriage 53 is positioned adjacent one end of the backup electrode, itwill be shifted along the bar 39 to adjacent the other electrode end.During such carriage movement, the rotating dressing wheel 55 willremove a portion of the damaged periphery of the backup electrode toexpose a new surface for use. The backup electrode 11 may now be rotatedslightly to position another worn or damaged electrode peripheryadjacent the dressing wheel 55 and the carriage 53 shifted intheopposite direction to thus dress another portion of the electrodeperiphery. The operations aforesaid may be continued until the entireperiphery of the backup electrode has been restored whereupon thehousing 54 will be returned to its full line position to await furtheruse, and welding may resume after the backup electrode 11 and thesupport 47 have been properly adjusted as hereinabove described.

While the backup electrode 11 has herein been shown and described asbeing round in cross section, it is to be understood that its workingperiphery may well provide a plurality of circumferentially spaced flatsfor cooperation with the roller electrode 10. Thus, such backupelectrode may be hexagonal or octagonal in cross section. Of course, itmayalso be provided with a greater or lesser number of flats asrequired.

We claim:

1. Resistance welding apparatus, including a pair of electrodes betweenwhich welding current may be passed through metal strips disposedtherebetween, one of said electrodes overlying said strips andselectively moveable thereagainst with welding pressure and also movablealong an elongated seam formed by overlapped edges of said strips toweld the strips along said seam, the other of said electrodes underlyingsaid strips and constituting a backup for said welding pressure, saidother electrode being elongated and disposed along the line of saidseam, the improvement comprising:

an elongated rigid bus bar underlying said strips and spaced from saidother electrode but extending parallel thereto, said bus bar beingelectrically connected to the secondary of the welding transformer;

a pair of brackets respectively connected to spaced longitudinal partsof said bus bar; and

a slide carried by each bracket for vertical adjustment, each slidebeing connected to said other electrode whereby the latter may bevertically adjusted, the connection between each slide and said otherelectrode permitting rotation of said other electrode about itslongitudinal axis so that various longitudinal faces of said otherelectrode may be presented to backup and weld said strips along saidseam.

2. The construction according to claim 1 wherein said other electrode isround in cross section.

3. The construction according to claim I wherein a wedge is held tosliding movement along a surface of each bracket and has an inclinedsurface engageable with a surface of a respective slide, and means formoving said wedges to cause vertical adjustment of said slides.

4. The construction according to claim 3 wherein a single shaft passesthrough both of said wedges and has threaded connection with each, saidshaft being held against axial movement, and means for rotating saidshaft.

5. The construction according to claim 4 wherein a bearing plate isconnected to each bracket and provides bearings for opposite ends ofsaid shaft.

6. The construction according to claim 4 and further including means forsupporting an intermediate portion of said other electrode againstdownward deflection which may be caused by said welding pressure, saidsupporting means comprising a housing, a saddle member adjustablevertically within said housing and having a saddle engaging anundersurface of said other electrode, and a further shaft for effectingvertical adjustment of said saddle member, said shaft being carried byone of said bearing plates.

7. The construction according to claim I and means for dressing alongitudinal surface of said other electrode, said dressing means beingcarried by said bus bar and selectively movable into engagement with asurface of said other electrode.

8. The construction according to claim 7 wherein said dressing meansincludes a carriage movable along said bus bar.

1. Resistance welding apparatus, including a pair of electrodes betweenwhich welding current may be passed through metal strips disposedtherebetween, one of said electrodes overlying said strips andselectively moveable thereagainst with welding pressure and also movablealong an elongated seam formed by overlapped edges of said strips toweld the strips along said seam, the other of said electrodes underlyingsaid strips and constituting a backup for said welding pressure, saidother electrode being elongated and disposed along the line of saidseam, the improvement comprising: an elongated rigid bus bar underlyingsaid strips and spaced from said other electrode but extending parallelthereto, said bus bar being electrically connected to the secondary ofthe welding transformer; a pair of brackets respectively connected tospaced longitudinal parts of said bus bar; and a slide carried by eachbracket for vertical adjustment, each slide being connected to saidother electrode whereby the latter may be vertically adjusted, theconnection between each slide and said other electrode permittingrotation of said other electrode about its longitudinal axis so thatvarious longitudinal faces of said other electrode may be presented tobackup and weld said strips along said seam.
 2. The constructionaccording to claim 1 wherein said other electrode is round in crosssection.
 3. The construction according to claim 1 wherein a wedge isheld to sliding movement along a surface of each bracket and has aninclined surface engageable with a surface of a respective slide, andmeans for moving said wedges to cause vertical adjustment of saidslides.
 4. The construction according to claim 3 wherein a single shaftpasses through both of said wedges and has threaded connection witheach, said shaft being held against axial movement, and means forrotating said shaft.
 5. The construction according to claim 4 wherein abearing plate is connected to each bracket and provides bearings foropposite ends of said shaft.
 6. The construction according to claim 4and further including means for supporting an intermediate portion ofsaid other electrode against downward deflection which may be caused bysaid welding pressure, said supporting means comprising a housing, asaddle member adjustable vertically within said housing and having asaddle engaging an undersurface of said other electrode, and a furthershaft for effecting vertical adjustment of said saddle member, saidshaft being carried by one of said bearing plates.
 7. The constructionaccording to claim 1 and means for dressing a longitudinal surface ofsaid other electrode, said dressing means being carried by said bus barand selectively movable into engagement with a surface of said otherelectrode.
 8. The construction according to claim 7 wherein saiddressing means includes a carriage movable along said bus bar.